Electrical protective apparatus



April 1, 1930.

w. WALTY 1,752,970

ELECTRICAL PROTECTIVE APPARATUS Filed Feb. 12 1926 yam/w;

Another object is the provision of appa- Patent ed Apr. 1, 1930 UNITEDSTATES PATENTOFFICE "WERNER WALTY, or ENNETBADEN, SWITZERLAND, ASSIGNORTO A. G. nnown novnnr & GIE. OE BADEN, SWITZERLAND, A JOINT-STOCKCOMPANY OF SWITZERLAND ELECTRICAL PROTECTIVE APPARATUS Application filedFebruary 12, 1926, Serial No. 87,853, and in Germany February 16, 192 5.

the efiects resulting from short-circuits etc. It has to do particularlywith the protection of respective generating or converting unitsinterconnected in a system.

The general object of the invention is the provision of apparatus forautomatically cutting out the unit affected and maintaining the desiredfunctioning of the others.

ratus for effecting this result, which will be immediate and certain inresponse and of simple and compact construction.

Other and further objects will be pointed out or indicated hereinafter,or become obvious to one skilled in the art upon an undera standing ofthe present disclosure. The particular arrangement here shown and degenerating or converting units, the short-cirscribed is presented forillustration only, and the invention may be embodied in apparatusdiffering therefrom in various particulars, all within the scope of theappended claims.

In the event of a short-circuit in one of the units of an electricalinstallation including cuit actsby way of the collectors or bus-bars onthe other units and causes all the main automatic switches to open.

the switches will not all be left open, ac-

cording to the present invention reverse current relays are interposedbetween the automatic switches and a collector or bus-bar, of.

I which relays only that in the circuit containing the defective orshort-circuited unit responds and prevents the opening of the automaticswitches of the sound units.

The accompanying drawing illustrates diagrammatically by way of exampleone em-.

bodiment of the invention.

Inthe drawing I, II, III denote three mercury vapour rectifiers of whichthe main current switches h 7?, k located in the continuous or directcurrent leads from the rectifiers, are controlled by .zero voltage coilsI 0 0 0 connected to an auxiliary source of the relative maximum currentor overload- I relays a a a, the coils of whlch IIlELXlHlIlIIl ofcurrent is. The circuit of each zero voltage coil contains the normallyclosed contacts In order that 5 current relays are located in the maincontlnuous current leads from the rectifiers I, II, III. The coils ofreverse current relays b b 6 are also located in the leads from therectifier-s between the main switches h 12 it and the bus-bar 9. Each ofthe reverse current relays b b 6 has switch contacts d, e, f, of whichthe contacts 6 and f are normally closed, the contacts cl being normallyopen. On passage of a return or reverse current the relays b 5 ,6respond,

direct current'sources 9 ,1 and j Referring more particularly to relay bthe arrangement is such that coil 2' tends to raise the; switch to itsupper position, the extent of excitation of this coil, however, beingsuch that the'same is not sufficient by itself to raise the switch tosuch position. During normal current'flow,the lower coil opposestheactionof coil i and has an influence on the switch tending to urgethe same down- Wardly. Upon the occurrence of reverse current flow,however, the action of the lower coil with respect to the switch isreversed,

the lower coil then acting with and supplementing the action of ,coil 2'to raise the switch to its upper position. The manner or principle ofoperation of relays Z2 and b is the same.

Assuming that there is a return surge in the rectifier II because of ashort-circuit, then all the three rectifiers work on the short circuit.The maximum current relays a a a all respond and open their contacts. Ofthe reverse current relays only 6 responds and opens its lower contacts6 and 7, and closes its upper contacts d. The closure of the uppercontacts (Z short-circuits the two auxiliary conductors 2', therebybridging the con tacts of the maximum current relays a a This willprevent the circuit. breakers 7L and it from tripping in spite of theresponsevof becomes currentless so that the switch a opens while theswitches h and it remain closed.

What I claim is:

1. In combination, an electric supply line,

a plurality of current sources connected in' parallel to said circuit, acircuit breaker for each of said sources for disconnecting the same fromsaid line, overload relay means associated with each circuit breaker fortripping the same in response to excess current flow from the respectivesource to said line,

and a reverse current relay means associated with each of said circuitbreakers for preventing tripping of the circuit breakers associated withthe sources to which no reverse current flow takes place, said relaymeans being so arranged that in absence of reverse current flow throughany one of said circuit breakers, overload in any of said circuitbreakers will cause the same to be tripped.

, 2. In combination, an electric supply line, a plurality of currentsources, leadsconnecting each of said sources to said line in parallel,circuit breakers in said leads for individually disconnecting saidsources from said line, overload relay means for individually trippingthe circuit breaker associated with the respective leads on occurrenceof overload therein, and reverse current relay means associated witheach of said leads for rendering inefl'ective the action of the overloadrelay means associated with the leads wherein no reverse current flowtakes place.

, 3. In combination, an electric supply line, a

normally closed double-pole switching con- "tacts for disconnecting theenergizing contacts of the associated tripping coil from said auxiliarydouble-pole line, and normally plurality of current sources, leads foreach of said sources for connecting the same to said line in parallel, acircuit breaker associated with each of said leads for disconnecting therespective sources from said line, a tripping coil for each of saidcircuit breakers, an overload relay associated with each of said leadsfor actuating the tripping coil of the associated circuit breaker todisconnect said source on occurrence of an overload in said lead, and areverse current relay in each of said leads, an auxiliary controlcircuit normally interconnecting the control contact-s of said overloadrelays of the several leads, the reverse current relay of each of saidleads having contacts operable to provide for disconnection of theassociated overload relay from said control circuit and interlockingauxiliary control contacts for said control circuit operable to providean interlocking circuit rendering ineffective the action of the overloadrelays of the leads that are free from reverse current flow.

4. In combination, an electric supply line, a plurality of currentsources, leads for each of said sources for connecting the same inparallel to said line, a circuit breaker in each of saidleads fordisconnecting said sources from said line, a no-voltage tripping coilfor each of said circuit breakers, an overload current relay associatedwith each of said leads, each overload relay having control contactsfornormally energizing the tripping coil of the associated circuitbreaker and being arranged to deenergize said circuit occurrence of anoverload, an auxiliary control circuit interconnecting the controlcontacts of the overload relays associated with the several leads, areverse current relay associated with each of said leads, each of saidreverse current relays having normally closed contacts operable toprovide for disconnection of-the associated overload relay from saidauxiliary control circuit and bridging contacts for said auxiliarycontrol circuits operable to provide an interlocking circuit bridgingthe control "contacts of the overload relays of the other circuitbreakers to prevent tripping of their respective circuit breakers.

5. In combination, an electric supply line,

a plurality of parallel feeders connected to "said line, a circuitbreaker associated with each of said feeders for disconnecting" the samefrom said line, a no-voltage tripping coil for each of said circuitbreakers having a pair of energizing contacts, an overload relayassociated with each of said feeders arranged tonormally hold closedsaid contacts and to open the same on occurrence of an overload, anauxiliary 2-pole'line interconnecting corresponding energizingcontactsof the several tripping coils, a reverse current relayassociated with each of said feeders, each of said reverse currentrelays having open bridging contacts for short circuiting said auxiliarydouble-pole line tobridge the energizing contacts of the tripping coilsas sociated with the other feeders. I

6. In an electrical system, a plurality of direct current supply lines,cut-out devices associated respectively with said lines and each beingresponsive to abnormal current conditions in the respective associatedline and being operable upon occurrence ofsuch conditions therein to cutout the same, control devices associated respectivelv with said linesand each being responsive to conditions of reverse current flow in therespective associated line, and connections providing-interlockingcircuits between said cut-out devices and said control devices and whichare effective upon operation of a control device, associated with one ofsaid lines to lock out of operation the cut-out devices associated withthe other of said lines.

In testimony whereof I have hereunto subscribed my name at Zurich,Switzerland, on

the 21st day of January, A. D. 1926.

WERNER WALTY.

